Process for the production of mechanical wood-pulp.



- G. 0. HOWARD. PROCESS FOR THE PRODUCTION OF MECHANICAL WQOD PULP. APPLICATION FILED AUG.31, 1911.

1,057,151, Patented Mari25,1913

Pa/p 607/1? 7071A lit afar l far k/aSs/W'e L V I I WITNESSES: 1 mmvrofi jg @4 a fim A TTOR/VEY -Washington, have invented certain new and useful Improvements 1n Processes for the -ent No. 997,064. In the "said patent- I de- .rnagnitpde between the balls of the several ,tube-mlllsand' the fiber-bundles being rea duced therein. In the progressive operation I of the mill the fibrous'contents are gradually .reduced to a relatively uniform size, in

- NITED STATES PATENT OFFICE.-

GUY C. HOWARD, OF SEATTLE, WASHINGTON.

PROCESS FOR THE PRODUCTION OF MECHANICAL WOOD-PULP.

v Specification of Letters Patent. J Patented Mar, 25, 1913,

Application filed August 81, 1911. Serial 1,! 0. 646,996.

To all whom it may concern:

Be it known that I, GUY G. HoWARD, a citizen of the United States, residing at Seattle, in the county of King and State of Production'of. Mechanical Wood-Pulp', of which the following is a specification.

This invention relates to improvements in processes for the production" of mechanical woodpulp and particularly to improvements. to the process disclosed ,in' my prior Patscribe a method of producing wood-pulp consisting of subjecting a'quantity of fiberbundles to disiptegrating action, as in a tube-mill containing balls of certain dimensions relative tothe sizes of said fiber-bundles and reducing the latter to a desired degree of fineness, subjecting the resulting reduced fiber-bundles to similar treatment by balls of reduced sizes,- and continuing in further like operation to reduce 6 sizes of said balls to correspond with the progressively reducing sizes of the fiber-bundles.

It is found that in the reduction of fibrous material by the methods outlined there is a considerable advantage in maintainin as far as practicable the predetermined ratio of which the fiber-bundles of an average or mean dimensions are suitable for introduction withinthe next mill in the series While a certainproportion of such material is of larger size than that intended for the economical operation of the. second mill and should advantageously be returned to the. original mill for further reduction. In like manner a quantity of the product of the first mill may be disintegrated to'a size smaller than that requisitefor the second" mill or perhaps may be suificiently reduced. to approximate the final desired product, in which case itwould be wasteful and con-.- trary to economical operation to subject the material -to further reduction. In the one case theaction of the balls ofthe second mill on material lar er than for which th y were intended woul result inin'efiicient p7. eration and in the lattencases material of proper final size or nearliy so would 'beacted upon to be furtherre uoed beyond a 'de-.

' returned to t sired minimum to the damage of the product by pulverization or undue shortening of the fiber-lengths and unnecessarily reducing the capacity of the a paratus by continued Working upon .a finished material.

It is the object of the present invention steps in the process and material upon whichthe reducing action has not been sufiiciently complete and hich may advantageously be quitted. I v j A- further object of the invention is to provide devices for classifying the product of the several grinding mills and automa'ti-- cally distributing the graded material to sub- 'theyare related and pass all smaller sized matter to other subsequent deviceswithout subjecting the same to further grindlng untll a mill inthe series is encountered treatlng materialof an approximate size. In the drawings accompanying thlS application, Figure 1 is a view in side elevation of apparatus employed in carrying out my invention. 2 1s a diagra-m'in plan of e grinding -mill recently a. pulp-producing plan't embodying the apparatus of my invention.

-I provide a plurality of fiber-separating and reducing machines designated by the reference numerals 1,2 and 3 respectively adapted to successively treat masses of fiberbundles in the rogressive stages of their reduction to a esired state of disintegration. These reducing machines are desirods herein shown will be equally advantageous when employed with machines of other modes of operation andwhen used singly -or in batteries of. machines in any number. Each said machine is provided with feed inlet 4 for" the introductionof fibrous material therein and an outlet {5 at the opposite end which is connected by a conveyor 6-to a suitable classifier 7 wherein the fiber-bundles constituting the partially ground pulp material are segregated into its) ably of'the ball or tube-mill type and while n I illustrate my process with a'serles of three 7 such machines," it is obvious that the methfit material comprising, respectively, fiberpassages through the .mills.

undles reduced to condition best suited for treatment by later processes and those fiberbundles still approximating in mass the predetermined size considered proper for treat-- ment in the mill just evacuated. Said classifier may be of any suitable type having the above-described functions. Those shown herewith are particularly described and illustrated in an application, Serial No. 646,997 filed simultaneously with the present one. For the purposes of thisapplication said devices may be described as each comprising a hopper 8 receiving said pulp material from the aforesaidrconveyer '6, a discharge '9 for the separated lighter fiberbundles and a tube 10 entering the lower portion of said classifier and containing mechanical means for conveying the heavier fiber-bundles to the adjacent mill. Each pulp mill is thus provided with a classifier whose elements are properly adjusted to separate the pulp issuing therefrom into classes respectively consisting of fiberbundles upon which the reducing action of the mill just encountered has not been sufficiently complete and that which is more suitable for treatment in succeeding steps. The latter product is conducted from the discharge 9 of the respective classifier by the duct 11 tothe charging hopper 8 of the next lower classifier in the serles Where it mingles with material emitted from the mill pertainingthereto and is again separated, as described. In this instance, however, the classifier is adjusted to discharge from its upper end only fiber-bundles of a size materially smaller than those released from the previously encountered classifier and subject for treatment in still further stage of the process while the opposite end retains -until conveyed 'away material suitable for reduction in the adjacent grinding machine, as 2. This cycle of operations is again repeated in the-third related group of machines and classifiers and in as many more similar groups as may be considered eifective.

"It-,will be noted that the material is not conveyed from one mill to another nor advisedly from aclassifier directly to'a mill,

but through. its-adjacent classifier. Thus a by-pass is createdfor the progressive movement of the pulp from its delivery from the first said mill in the" series exteriorly of the H Fibers that may be reduced to a desired degree of disintegration in the first or succeeding mills are successively passed from one classifier.

to the next without bein'gcaused to undergo further' grinding in the .mills. finally-delivered at'the final completed stage in the desired state of disintegration without j he It is thus.

ening of fiber length and without unnecessarily occupying space within the mills and clogging their efiicient action. The passage of the pulp through the several said machines and classifiers is practically automatic in its action of grading and classifymg.

The classifiers are adjusted to retain and return to their proximate grinding machines such fibrous matter as may be determined to besuitably adapted to be "round by such machine in the process and all matter of smaller sizes passes on to be acted upon by similar devices regulated at the will of the operator.

The process, as outlined, produces essentially a so-called mechanical pulp as distinguished from a chemical pulp and which is used in large quantities in making certain grades of paper, box-board, etc.

The advantages of the process are that it permits of an increased capacity of the grinding machines as it eliminates a large amount of unnecessary grinding and it althe mill just evacuated, conducting the remaining material through a second classifier arranged to select material of certain reduced sizes and deliver same to a mill adapted to treat material of said approximate size, passing the remainder to a suecessive classifier, receiving in turn the discharge of the second named mill .for similar classification. i

2. The process of treating fibrous vegetable material consisting of grinding same in a series of mills each adapted to treat material of progressively reduced sizes, passing the output of the first mill through a classifier arranged to extract the material that has been sufiiciently reduced and returning the latter to the mill just evacuated, conducting the remaining material through successive classifiers until discharged as finished pulp or selected by aclassifier for further reduction by a-mill of the series.

3. ,The process of manufacturing ..woodpulp consistin ofipassing partially reduced fibrous vegeta le material through a series of classifiers each adapted to separate material of a predetermined size to deliver same to a inding mill arranged to treat pulp material of the respective sizeand to deliver material of smallersize to following classifiers in the series for relatively similar sepa ration and delivery.

4. A process for treating material to be ground to uniform size consisting in providing a series of grinding mills each adapted to grind material of progressively diminishing sizes, passing partially ground material fromieach mill through a classifier adapted to extract and return material insufliciently ground to the respective mill and continuing the remainder'throu h successive classifiers of progressively reducing selective adjustment each of which is adapted to extract material of predetermined minimum size and deliver same to a mill arranged to treat material of said approximate size.

5. The process of treating fibrous vegetable material consisting of partially grinding said materialin a mill, introducing said partially ground pulp in a series of classifiers each of which is arrangedto extract particles of the material, of "predetermined minimum size and passing the remainder to the next classifierin the series, the material thus extracted being conducted to mills for regrinding adapted to treat material of the respective approximate sizes.

6. A process of manufacturing wood-pulp consisting in providing a series of pulp- .grinding mills each adapted to treat material of different sizes and provided with a classifier connected with its discharge end, returning the heavier particles from each classifier to the mill just evacuated, and delivering the lighter particles to the next sized classifier in the series.

7. A process .of producing wood-pulp consisting in grinding fibrous vegetable material in a mill, discharging same into a classifier adapted to separate the material into relatively heavier and lighter grades, returning the heavymaterial to the mill just evacuated for regrinding and delivering the lighter material to amill adapted to work upon material of such grade.

8. A process of producing wood-pulp consisting in grinding fibrous vegetable material in a m1ll, discharging same into a classifier adapted to separate the ,material into relatively heavier and lighter grades, returnlng the heavy material to the mill just evacuated for regrinding and delivering the lighter material through another classifier to a mill adapted to work upon material of such grade.

' 9. In apparatus for carrying out the herein-described process, a series of grinding mills adapted to treat material of predetermined progressivelyreduced sizes, a classifier connected to the discharge of-each said mill to receive the partially ground contents ofits respective mill and selectively grade and return to said mill for regrinding material approximatin in size that for which said mill is particu arly adapted and means to convey the remaining material through the successive classifiers of the serles and such other mills only as are adapted to treat.

the approximate sized material.

10. In apparatus for carrying out the herein described process, a grinding mill'- particularly adapted to treat material of a predetermined size, and a classifier provided with a feed-inlet communicatively connected with the discharge of said mill, said classifier arranged to return to said mill for regrinding material approximating said predetermined size and eliminating material of sufficiently reduced size.

' 11. In apparatus for carrying out the herein-described process, a plurality of grinding mills each provided'with a classlfier whose feed-inlet is communicatively connected with the discharge end of the respective mill and whose larger classified material is arranged to be returned to the feed-inlet of said mill, and communicative connections between the several classifiersarranged to transfer the smaller classified material of a classifier to the feed-inlet of the next suitable classifier in the series.

12. In apparatus for carrying out the herein-describedprocess, the combination of aseries' of grinding mills each adapted to treat material of certain approximate size,

a classifier for each said mill rovided with a feed-inlet, a discharge for light material, and a discharge for heaviermaterial, communicative connections between the dismaterial of each classifier and the feed-inlet of the respective mill, and communicative connections between the discharge of the lightermaterialof a classifier and the feedinlet of the next classifier in the series.

13. In apparatus 'for "carrying out the herein-described process, a series of grinding mills adapted to treat material of predetermined progressively reduced sizes, a classifier for each' said mill adapted to. receive the partially ground contents of its respective milland gradedmaterial from previousclassifiers in the series, said classifier arranged to.selecti'vely grade said materlal and deliver to its respective mill the separated material approximatingthe size for which said mill is adapted and deliver the remaining material tb lower classifiers in 

